In offshore drilling operations in deep water, the operator will perform drilling operations through a drilling riser. The drilling riser extends between the subsea wellhead assembly at the seafloor and the drilling vessel. The drilling riser is made up of a number of individual joints or sections. These sections are secured to each other and run from a riser deploying floor. The drilling riser also normally has a number of auxiliary conduits that extend around the main central pipe. The auxiliary conduits supply hydraulic fluid pressure to the subsea blowout (preventer and lower marine riser package. A recent type of drilling riser does not require auxiliary lines spaced around it. That type of drilling riser is built to withstand high pressure, and the blowout preventer is located on the drilling rig.
The central pipe of a drilling riser joint has a pin member on one end and a box member on the other end. The pin of one riser joint stabs into the box of the next riser joint. In one type of riser joint, flanges extend outward from the pin and box. The operator connects the flanges together with a number of bolts spaced around the circumference of the coupling. In another type of riser, individual segments or locking segments are spaced around the circumference of the box. A screw is connected to each locking segment. Rotating the screw causes the locking segment to advance into engagement with a profile formed on the end of a pin.
In these systems, a riser spider or support on a riser deploying floor moves between a retracted position into an engaged position to support previously made-up riser joints while the new riser joint is being stabbed into engagement with the string. Wave movement can cause the vessel to be moving upward and downward relative to the riser.
In both types of risers, workers use wrenches to make up the bolts or screws. Personnel employed to secure the screws or the bolts are exposed to a risk of injury. Also, making up the individual bolts is time consuming. Often when moving the drilling rig moving the drilling rig from one location to another, the riser has to be pulled and stored. In very deep water, pulling and rerunning the riser is very expensive. At least one automated system is shown in U.S. Pat. No. 6,330,918 for making up riser locking segment screws.